This invention relates generally to hydraulic pumps, and more particularly to centrifugal pumps for pumping hot liquid under pressure.
Prior centrifugal pumps have generally had a casing containing a main flange to form an enclosed area for the liquid to be pumped, and a cooler, bearing assembly, and seals all mounted above the main flange area of the pump structure. The location of these elements required an expensive casing and a relatively long pump structure. In order to minimize costs, it is desirable to position the seals, bearings, and coolers beneath the main flange area within the casing. In this location, these elements are generally surrounded by the hot liquid, and means must be utilized to thermally insulate these elements.
Thermal barriers have generally been inserted into the casing surrounding the shaft, and its associated elements, to prevent the hot liquid from coming in contact with the elements, and to thermally insulate them. These thermal barriers have generally included either an insulation material sheathed in a metallic casing, or concentric, spaced apart cylinders. These types of thermal barriers have not proven effective, especially for large centrifugal pumps where difficulties in fabrication are encountered.
Additionally, another problem occurs with these types of thermal barriers. The thermal expansion of these barriers between the high temperature side and the low temperature side, and the relative expansion therefrom, causes shearing forces. Because these barriers are held securely in position, these shearing forces have caused cracking and deformation problems.